Why I bleed after sex

Treatment of bleeding after sex :
the treatment depends on the cause so you should visit the doctor and doing clinical examination , we advice to stop sexual activity during treatment and keep the genital area clear , and if there is bacterial infection you can use Metronidazole 500mg 2 times daly for 10 days , and in the event of vaginal dryness, you can use estrogen compounds under medical supervision 
Diagnosis :
By taking full medical history and doing clinical examiantion , and CBC to detect infection and Pelvic ultrasound , and Urine analysis , and vaginal and cervical examination by  spiculum 
Causes :

• Genital injury 
• Vaginal dryness
• Infections
• Cervical or endometrial polyps
• Fibroids
• Endometriosis
• Anatomical abnormalities

Advice : 
you should visit the Gynecologist to get proper managment